1. Field of the Invention
The present invention relates to a tamping tool unit for tamping ballast under a respective one of successive ties of a railroad track, which comprises a frame extending in a frame extending in a longitudinal direction, a pair of tamping tool levers mounted on the frame for pivoting about a pivot axis in a plane extending in the longitudinal direction, a reciprocating drive connected to each tamping tool lever for pivoting the tamping tool lever, and a tamping pick at a lower end of each tamping tool lever.
2. Description of the Prior Art
Such tamping tool units are well known, and U.S. Pat. No. 4,576,095 discloses such a tamping tool unit wherein the opening width of a pair of reciprocating tamping tool levers may be selectively varied, which may be necessary, for example, if a double tie is to be tamped by the pair of reciprocating tamping tool levers. For this purpose, a stop pivotal into engagement with the piston rod of the reciprocating drive may be actuated to change the reciprocating path. In this way, the tamping tool unit may be adapted to different crib widths.
In the tamping of ballast under successive ties of a railroad track, the crib width, i.e. the distance of the ties from each other, is of essential importance. If, for instance, a track to be tamped changes from wooden to concrete ties, the resultant change in the crib width causes considerable problems in a continuous track tamping operation. Normally, this has required a different tamping unit whose tamping picks are adapted to the changed crib width.